Eddy current couplings having a variable output speed are well known in the art. An example of such a coupling is disclosed in U.S. Pat No. 4,476,410 and in copending application Ser. No. 065,118 filed Jun. 22, 1987, now U.S. Pat. No. 4,780,637. Both the patent and application are expressly incorporated herein by reference.
Eddy current couplings which are known in the art may be equipped with a brake assembly for braking rotation of the output shaft. In the past, an eddy current brake has been mounted on the housing of the eddy current coupling coaxial to the output shaft. The brake in the prior art would be connected to the output shaft to effect braking thereof. When the field coil of the brake is energized the output shaft of the eddy current coupling will be braked.
In at least one prior art construction, the inductor of the eddy current brake which was attached to the output shaft of the eddy current coupling, revolved within the stationary pole assembly. An air gap is maintained between the stationary pole assembly and the inductor drum. The magnitude of the air gap is small in order to provide efficient coupling between the inductor and pole assembly. In some of the known prior art construction, the heat generated during energization of the brake resulted in the expansion of the brake members thereby causing the inductor drum to heat and expand into physical contact with the pole assembly thereby degrading the operation of the brake assembly. In addition, the known prior art brake mechanisms utilized specially manufactured parts to brake the output shaft of the eddy current coupling.